1. Field of the Invention
The present invention relates to a method for manufacturing a composite rubber tire, and more particularly to a composite rubber tire that has a polyurethane tread to achieve an environmentally friendly tire with excellent mechanical efficiency.
2. Description of Related Technology
Environmentally friendly tires mostly refer to radial tires that have less rolling resistance to reduce vehicles fuel consumption and exhaust, and to reduce the waste gas ejected. By using environmentally friendly tires, rolling resistance is reduced by 22-25%, and fuel consumption is reduced by 3-8%. Therefore, research into environmentally friendly tires is a popular subject for tire manufacturers worldwide.
Environmentally friendly tires have been developed for decades and are basically classified into two types: natural rubber radial tires and molded polyurethane tires. Natural rubber radial tires have an internal body and an outer surrounding layer. The internal body and the outer layer are made of natural rubber. The natural rubber radial tires have excellent kinetic properties such as low heat generation and good flexibility and are suitable for use as high-speed tires. Natural rubber radial tires usually are coated with an improving glue on the outer surface to reduce the rolling resistance and to strengthen the tires. Current third generation radial tires have a rolling resistance 30% less than first generation radial tires. However, nature rubber tires still have the following drawbacks:
1. Natural rubber radial tires do not have good wear-resistance. Although an improving glue is applied to the outer surface of natural rubber radial tires to reduce rolling resistance, the improving glue reduces the wear-resistance. Therefore, the natural rubber radial tires are not durable and must be replaced and discarded often, which causes more trash problems. Additionally, abrasion of the natural rubber radial tires also causes environmental problems such as releasing metal particles into the air. For example, dust beside highways contains 42 times the zinc contamination, 28 times the copper contamination, 19 times the chromium contamination and 8 times the lead contamination than in parks.
2. Because natural rubber radial tires are less durable, the improving glue contains carbon black and carcinogenic aromatic oil to enhance the durability. Both additives are released into the environment and cause more pollution.
Therefore, the natural rubber radial tires are not actually environmentally friendly. With increasing attention to environmental protection, manufacturers have started to focus on using non-pollutants and apply a new improving glue on the tire to reduce rolling resistance. Furthermore, the manufacturers also want to increase the wear-resistance of the tire to improve tire durability to reduce the quantity of waste tires and to reduce heavy metal pollutants released into the environment.
Molded polyurethane tires have an internal body and an outer surrounding layer. The internal body and the outer layer are made of polyurethane.
The polyurethane tire has excellent wear-resistance that makes the tire durable and overcomes the problem of an excessive number of discarded tires. Furthermore, the polyurethane tire is very strong and does not need either carbon black or aromatic oil as additives. Therefore, the polyurethane tire has no environmental problems caused by the additives.
However, the polyurethane tire still has the following drawbacks.
1. The polyurethane tire is very hard and has less flexibility than the nature rubber tire and poor kinetic properties. Therefore, the polyurethane tires have high rolling resistance that causes excessive heat in the tires and the engine, which causes increased oil consumption in the engine, and polyurethane tires are not suitable for use as high-speed tires.
2. Furthermore, the polyurethane tire has several complex manufacturing problems such as a complex core mold structure, location of a rim, preparation of a reinforcing fabric and location of the reinforcing fabric that increase operating cost of the polyurethane tire.
The present invention has arisen to mitigate or obviate the disadvantages of the conventional environmental friendly tire.